Method of destroying sewage



Dec. 6, 1938. H' MORETQN 2,139,419

METHOD OF DESTROYING SEWAGE Filed Aug. 19, 1935 Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE METHOD OF DESTROYING SEWAGE v Henry H. Moreton, Santa Monica, Calif.

Application August 19, 1935, Serial No. 36,933

8 Claims.

This invention is a method effecting complete destruction of sewage.

The effective destruction of sewage without soil or water pollution has long been a serious 5 problem. In fact, attempts heretofore made to physically destroy sewage have met with indifferent success from the standpoint of practical economy and convenience in handling, and at the present time, the so-called bacterial systems are considered the safest and most desirable methods for municipal installations. A system of the last-mentioned type, however, involves the installation of apparatus which must be spread over a considerable area, requires a very large investment to meet the initial cost of installation, and is more or less expensive to operate.

One of the objects of the invention is to provide for complete and economical physical destruction of sewage by incineration, whereby practically no residue is left, so that the possibility of either soil or water pollution is reduced to the absolute minimum. A further object is to provide for complete incineration of sewage in such manner that the discharge of objectionable and offensive odors, smokes and gases into the surrounding atmosphere is prevented. A further object is to provide a system of low installation cost and highly economic operation, capable of providing for initial dehydration of the sewage and subsequent complete incineration in a continuous process. A further object is to employ the caloric values inherent to the sewage being treated, to assist in the incineration of the material being treated, after its dehydration.

The invention will be hereinafter fully set forth and particularly pointed out in the claims.

In the accompanying drawing:

Figure l is a vertical elevation more or less diagrammatic in character, illustrating an appara tus constructed in accordance with the invention, certain parts being shown in section. Figure 2 is a detail sectional view of a portion of one of the rotatable furnaces.

Referring to the drawing, I designates a combined dehydrator and incinerator, which consists of a reltaively long cylindrical chamber Ill, rotatively supported in a longitudinally inclined position, in a well known manner, by suitable bearings l I. Rotation of the cylindrical chamber may be effected by any suitable means, such as a gear l2 engaging a gear-ring l3, which encircles the cylinder Ill. The higher end of said cylinder l projects into a receiving chamber l4, through the top of which extends an inlet chute Ni.

The open lower end of the cylindrical chamber Ill extends into a burner box 20, into which is projected one or more burners 2| for gas, oil, or

the like, the delivery ends of the burners being directed axially toward the incinerator I, in such 5 manner as to project the flame into the open lower end of the latter. The burner casing rests upon a suitable platform 22, onto which the chamber l0 deposits the material which is discharged from the lower end thereof, said platform having a chute 23, which communicates with the interior of a filter chamber F. It will be observed that the incinerator chamber III is provided with an annular bafile 29, which is spaced a suitable distance from the delivery end of the chamber. The products of combustion are discharged from the incinerator into a stack 8.

The filter chamber may be of any desired construction, being preferably a gravity filter provided with a filter bed I of sand or a similar material, resting upon a perforated supporting plate I, and having a discharge spout for eiliuent. Said filter chamber F is provided with a trap for sand, controlled by a suitable valve. Immediately above the filter bed and centrally disposed with respect to chute 23 is a conical spreader i Leadinglaterally from the filter chamber F is a conveyor f of any desired structure, such as the screw-type, having a discharge chute which communicates with the interior of a mixing apparatus 24, operated by a suitable motor 25. The mixing apparatus may be of any suitable or desired construction, such as the common type of apparatus usually employed for mixing concrete. Any gases which may accumulate in the top of the filter chamber F are drawn out by the blower l5 and delivered to the burner box 20, so that they may be burned and thereby assist the operation of the burners. Any gases which may accumulate within the mixing apparatus 24 are withdrawn by a blower I5 and also delivered in a similar manner to the burner box. Said gases are trapped by the bafile 21. The mixture is discharged from the mixer 24 through a spout 28 onto a conveyor C, which elevates the mixture to a point where it may be discharged into the chute l5 and again into the chamber I0. In the course of time sand will accumulate in the bottom of the filter chamber. This accumulated sand may be withdrawn through trap I and transferred by a conveyor 0' to a conveyor 0.

Located in a convenient position adjacent to the apparatus thus far described is .a suitable storage tank III for thqsewage, which is preferably in the form of sludge. Leading from the lower portion of said tanfira discharge pipe Ii. which delivers sludge to a pump 82, by which the sludge is delivered to the filter chamber 1'', through a pipe 32.

In operation, assuming that the burners 2| are lighted and in operation, and initial charge of sand or similar inorganic granular material, capable of withstanding high temperature without fusing, is introduced into the chamber I through the chute l0. It is preferred to use good sharp silica sand, and a suiiicient quantity must be initially introduced to insure continuing cycles of operation in a manner about to be described. As the sand is introduced into the chamber I0, the latter is rotated, causing the sand to travel slowly down through the chamber toward the lower end, so that it will be agitated, and also receive a high temperature due to the heat generated by the burners 2|. The burners are directed toward the downwardly fiowing material in a manner adapted to impart a relatively high temperature to the sand, but the heat must be regulated so as to avoid fusing temperatures, because fusing of the sand particles would greatly impair the operation.

The apparatus will be primed for operation at the time that the chamber l0 begins to discharge sand from the lower end thereof. As the heated sand is discharged from the incinerator, it is deposited on the top of the filter bed i. At the same time, sewage is being supplied from the tank ill into the chute 23. so that there is a preliminary inter-mixture of sewage with heated sand as the sewage is deposited upon the filter bed. The mixture of sewage and sand is withdrawn from the chamber F by means of a'conveyor I. The conveyor may be of any desired type, a common form of screw conveyor being diagrammatically shown for purposes of illustration. The degree of inclination of said conveyor and the extent to which it must project into the filter bed I are matters to be determined at the time of installation, the conveyor being illustrated diagrammatically and without intent to limit the design or the details of installation. During the period of time that it takes for the mixture to travel from the chute 23 to the conveyor I, there is a partial dehydration of the mass, but a very substantial quantity of the water content of the sewage will filter out through the filter bed I, and the eiliuent may be discharged through the outlet P, or conducted to any desired point of delivery. Sand removed by conveyor f is replaced by heated sand supplied through chute 23.

It is desirable to obtain a much more thorough intermixture of the sand and sewage than the preliminary intermixture thereof. before incineration. Therefore, the conveyor f discharges the residual mixture of sand and filter sewage into the mixer 24, where the two materials are intermixed, and by reason of the pressure created by the mixer blades are discharged upwardly, back of the bai'lle 21, and outwardly through the spout 29 to the conveyor C, which elevates the mixture to such a position that it may be discharged into the chute l6 and from there carried into the incinerator 1. After being subjected to the operations above described, the sand particles will be coated with colloidal portions of the residual sewage constituents. As the mass of coated refractory particles continues its travel toward the lower end of the incinerator, said mass passes through a heated space within which it is subiected to a gradually increasing temperature as it approaches the discharge end of said incinerator. Therefore, almost immediately after the mixture enters the incinerator the temperature is sufficiently high to dehydrate the coatings and during the travel of the mixture the temperature is sufiiciently increased to ignite the dehydrated organic material without fusing the refractory material, and incineration of the organic constituents is completed by the time the granular carrier material reaches the discharge end of said chamber and immediately before it is deposited upon the filter bed I, with another charge of sewage. From this point, the cycles become continuous and automatic, the sand being passed through the mixing and dehydrating stages, and being continuously mixed with new sewage within the filter chamber F. As dehydration and incineration take place during the travel of the mixture through the chamber l0, combustible gases are given off, which are ignited by the heat within the cylinder, and the same is true of the fumes delivered by the blower I5. These gases aid in the combustion of the dehydrated residual material. The products of combustion pass to the stack through the flue 26. Should it be necessary fresh sand may be added to the original charge from time to time.

The advantages of the invention will be readily apparent to those skilled in the art to which it belongs. An important advantage is that by reason of the filtration of the sludge and the removal of a substantial part of the moisture content by this means, the period of time and the temperatures required for the dehydration and incineration are materially reduced. Another advantage ls that the sand adsorbs such moisture content as remains with the sludge during the passage of the mixture through the incinerator, thereby creating a condition which makes it easy to so control the passage of the mixture through the chamber that even dehydration is effected. Therefore, after the apparatus is once put into operation and the first cycle has been completed, less heat is required at the burner end than would otherwise be required, thereby reducing the chances of fusing the sand and yet insuring that the sand when it leaves the incinerator will be in a condition for immediate mixing with more sludge, so that a continuous hot sand cycle is provided. Another advantage is that as the sludge and sand mixture enters the chamber l0, it will first give off its moisture near the upper end of said chamber and later will be completely incinerated as it approaches the lower end of the chamber, the combustible gases given off during this stage being capable of developing sufficient B. t. u.s to very materially aid in the destruction of sewage introduced during subsequent cycles. Another advantage is that the mixture of sand and sewage travels in a general longitudinal path, and that the burners project their fiames in lines parallel with said path and at the terminal end thereof, so that the hottest zone in the incinerator is adjacent to its annular internal baffle.

Having thus explained the nature of the invention and described an operative manner of constructing and using the same, although without attempting to set forth all of the forms in which it may be made, or all of the forms of its use, what is claimed is:

1. A method of destroying sewage comprising removing liquid from sewage by depositing sewage and hot inorganic granular material upon a filter bed, removing the inorganic granular material and residual sewage and intimately mixing the same, and heating the mixture to such a temperature as will incinerate the residual sewage.

2. A method of destroying sewage comprising removing liquid from the sewage by depositing sewage and hot inorganic granular material upon a filter bed, removing the residual sewage and granular material, and intimately mixing the same, and causing the mixture to travel through a calcining zone maintained at a temperature sufficiently high to effect incineration of the sewage.

3. A method of destroying sewage comprising removing liquid from sewage by depositing sewage and hot inorganic granular material upon a filter bed, removing the residue and intimately mixing the same, incinerating the sewage content of the mixed residue by causing the mixture to travel from one location to another in a general longitudinal direction and agitating it during its travel, temporarily arresting progress of the mixture before it reaches the end of its travel so as to create a thickened and constantly agitated bed of mixed hot sand and sewage, and maintaining said body at approximately uniform volume by means of a continuing supply of the mixture.

4. A method of destroying sewage comprising depositing a mixture of sewage and heated inorganic granular material upon a bed of similar inorganic granular material, whereby some of the liquid content of the sewage will be filtered off and the remaining liquid content partially evaporated by the heated material, and then completely destroying the organic constituents of the mixture by the application of heat at sufllciently high temperature to effect incineration of said organic constituents without destruction of said granular material.

5. A method of destroying sewage comprising providing a heated mixture of sewage material and a refractory non-absorbent hot granular material, effecting 'partial dehydration of the hot mixture by filtration, causing the partially dehydrated mixture to travel through a heating zone maintained at a temperature below the fusing point of said granular material, and completely destroying the sewage constituents of the mixture by causing the mixture during the recycling stage to travel through a heated zone maintained at a temperature sufficiently high to eflect combustion of said sewage constituents and discharging the sewage-free refractory material from said heated x1e in an approximately unchanged granular to. i

6. A method of destroying sewage comprising heating a refractory non-absorbent granular material to a high temperature by causing it to travel through a heated zone maintained at a temperature below the fusing point of said material, mixing sewage with the hot granular material as it is discharged from said heating zone, partially dehydrating the hot mixture by filtration, recycling the residual mixture through said heating zone, and completely destroying the residual sewage constituents by causing the mixture during the recycling stage to travel through a heated zone maintained at a temperature sufficiently high to effect combustion of said sewage constituents and at the end of said recycling stage discharging the sewage-free refractory material from the heated zone in an approximately unchanged granular state.

7. A method of destroying sewage comprising heating a refractory non-absorbent granular material to a high temperature by causing it to travel through a heated zone maintained at a temperature below the fusing point of said ma-' terial, mixing sewage with the hot granular material as it is discharged from said heating zone, partially dehydrating the hot mixture by filtration, recycling the residual mixture through said heating zone, and completely destroying the residual sewage constituents by causing the mixture during the recycling stage to travel through a heated zone maintained at a temperature sufficiently high to efi'ect combustion of said sewage constituents at the end of said recycling stage discharging the sewage-free refractory material from the heated zone in an approximately unchanged granular state, and increasing the temperature of the inorganic material as it approaches the end of each travel through said heating zone.

8. A method of destroying sewage comprising heating a high-temperature-resistant inorganic material by causing it to travel through a heating zone, recycling said material through said heating zone, mixing sewage with the previously heated inorganic material subsequent to the initial heating and prior to the recycling stage, removing liquid from the mixture by depositing the latter upon a filter bed, removing the residual mixture and inorganic material from the filter bed and then more intimately mixing them, and finally completely destroying the sewage residue by causing the mixture during the recycling stage to travel through a heated zone maintained at a temperature sufficiently high to eifect combustion of said sewage constituents.

HENRY H. MORETON. 

